The present invention relates to construction equipment, such as crawler cranes, which must be disassembled into a number of components to be transported between job sites. In particular, the present invention relates to a removable connection for connecting each of the crawlers to the carbody of the crawler crane. The present invention also relates to a method of connecting (and disconnecting) each of the crawlers to (from) the carbody of the crane.
Construction equipment, such as cranes or excavators, often must be moved from one job site to another. Moving a crane or an excavator can be a formidable task when the machine is large and heavy. For example, highway limits on vehicle-axle loads must be observed and overhead obstacles can dictate long, inconvenient routings to the job site.
One solution to improving the mobility of large construction machines, such as cranes, is to disassemble them into smaller, more easily handled components. The separate components can then be transported to the new job site where they are reassembled. For example, the typical practice has been to disconnect, remove, and transport the crawlers separately from the crane.
In conventional cranes, each of the crawlers is typically bolted to the carbody of the crane. Because the connections between the crawlers and the crane carbody must sustain tremendous loads, the size and number of bolts used in these connections can be substantial. Accordingly, removing each of the crawlers from the carbody of the crane usually requires the loosening and removal of numerous large bolts from each of the crawler to carbody connections. Once the crane components are delivered to the new job site, then the crawlers must be carefully aligned with the carbody, and each of the bolts must then be re-inserted and tightened for each of the crawler to carbody connections. As a consequence, the disconnection and re-connection of the crawlers to the crane can be a difficult and time-consuming process.
One attempt to overcome some of the above-described problems is disclosed in U.S. Pat. No. 5,823,279 to Petzold, entitled “Carbody to Crawler Connection”, which issued Oct. 20, 1998. This patent discloses a carbody to crawler connection that utilizes a pair of pins. A vertical pin extends upwardly from the horizontal flange on the top of the carbody arm and is configured to loosely engage a hole in the horizontal flange on the top of the crawler frame weldment. A horizontal pin passes through lower portions of the vertical flanges of the carbody arm and the vertical flange of the crawler frame weldment. The crawler is attached to the carbody by first placing the hole in the horizontal flange on the top of the crawler frame weldment over the vertical pin on the top of the carbody arm. The hole in the vertical flange of the crawler frame weldment is then aligned with the holes in the vertical flanges of the carbody arm. The horizontal pin is then inserted through these holes so as to complete the connection.
The carbody to crawler connection disclosed in U.S. Pat. No. 5,823,279 has several advantages over the bolted-type connections typically used in conventional cranes. For example, this type of connection eliminates the need to carefully align and fasten numerous bolts. However, this type of connection is not suitable for larger cranes. In particular, the forces generated between the carbody to crawler connection in larger cranes can cause the connection components to deflect and become misaligned with respect to each other. For example, the arms of the carbody may twist or spread outwardly as a result of eccentricities in the forces between the carbody and the crawlers. The carbody to crawler connection may even fail if the deflection and misalignment in these components is large enough.
The degree of deflection and misalignment can be further aggravated by the use of high strength steel, which is often used for larger cranes. This is because high strength steel has the same modulus of elasticity as lower strength steel. As a result, the higher loads that components using high strength steel are designed to accommodate will necessarily cause higher deflections.
To prevent the deflection and misalignment of the carbody to crawler connection components in larger cranes, the arms one each side of the carbody have been typically connected together so as to form a box-like structure. However, the use of plates or cross-bracing between the carbody arms can add significant weight and manufacturing costs to the crane. Plates or cross-bracing between the carbody arms can also inhibit access to portions of the crane, and can make the disconnection and re-connection of the crawlers to the crane more difficult.
It is therefore desirable to provide an improved carbody to crawler connection that facilitates a simple and time-efficient disconnection and re-connection of the crawlers to the crane, that will not deflect or become misaligned as a result of forces generated between the carbody to crawler connection components, and does not require the use of plate structures or cross-bracing between the carbody arms.